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tftpd: allow a rewrite rule to probe for the existence of a file

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This adds an "E" flag to the rewrite rules, which exits rule
processing if and only if the result is a valid, accessible
filename. If combined with "r", the rewrite is cancelled if the rule
is not applied.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
H. Peter Anvin 2024-05-29 17:16:06 -07:00
parent 1dc6d55811
commit 6f96fcd1b6
5 changed files with 103 additions and 47 deletions
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72
tftpd/remap.c
View file

@ -1,6 +1,6 @@
/* ----------------------------------------------------------------------- *
*
* Copyright 2001-2014 H. Peter Anvin - All Rights Reserved
* Copyright 2001-2024 H. Peter Anvin - All Rights Reserved
*
* This program is free software available under the same license
* as the "OpenBSD" operating system, distributed at
@ -34,6 +34,8 @@
#define RULE_IPV4 0x40 /* IPv4 only */
#define RULE_IPV6 0x80 /* IPv6 only */
#define RULE_HASFILE 0x100 /* Valid if rule results in a valid filename */
struct rule {
struct rule *next;
int nrule;
@ -213,6 +215,9 @@ static int parseline(char *line, struct rule *r, int lineno)
case 'e':
r->rule_flags |= RULE_EXIT;
break;
case 'E':
r->rule_flags |= RULE_HASFILE;
break;
case 's':
r->rule_flags |= RULE_RESTART;
break;
@ -244,15 +249,21 @@ static int parseline(char *line, struct rule *r, int lineno)
}
}
/* RULE_GLOBAL only applies when RULE_REWRITE specified */
if (!(r->rule_flags & RULE_REWRITE))
r->rule_flags &= ~RULE_GLOBAL;
if ((r->rule_flags & (RULE_INVERSE | RULE_REWRITE)) ==
(RULE_INVERSE | RULE_REWRITE)) {
syslog(LOG_ERR, "r rules cannot be inverted, line %d: %s\n",
lineno, line);
return -1; /* Error */
if (r->rule_flags & RULE_REWRITE) {
if (r->rule_flags & RULE_INVERSE) {
syslog(LOG_ERR, "r rules cannot be inverted, line %d: %s\n",
lineno, line);
return -1; /* Error */
}
if ((r->rule_flags & (RULE_GLOBAL|RULE_HASFILE))
== (RULE_GLOBAL|RULE_HASFILE)) {
syslog(LOG_ERR, "E rules cannot be combined with g, line %d: %s\n",
lineno, line);
return -1; /* Error */
}
} else {
/* RULE_GLOBAL is meaningless without RULE_REWRITE */
r->rule_flags &= ~RULE_GLOBAL;
}
/* Read and compile the regex */
@ -333,12 +344,14 @@ void freerules(struct rule *r)
}
/* Execute a rule set on a string; returns a malloc'd new string. */
char *rewrite_string(const char *input, const struct rule *rules,
char *rewrite_string(const struct formats *pf,
const char *input, const struct rule *rules,
char mode, int af, match_pattern_callback macrosub,
const char **errmsg)
{
char *current = tfstrdup(input);
char *newstr;
const char *accerr;
const struct rule *ruleptr = rules;
regmatch_t pmatch[10];
int len;
@ -410,13 +423,34 @@ char *rewrite_string(const char *input, const struct rule *rules,
newstr = tfmalloc(len + 1);
genmatchstring(newstr, ruleptr->pattern, current,
pmatch, macrosub);
free(current);
current = newstr;
if (verbosity >= 3) {
syslog(LOG_INFO, "remap: rule %d: rewrite: %s",
ruleptr->nrule, current);
}
}
if ((ruleptr->rule_flags & RULE_HASFILE) &&
pf->f_validate(newstr, mode == 'G' ? RRQ : WRQ,
pf, &accerr)) {
if (verbosity >= 3) {
syslog(LOG_INFO, "remap: rule %d: ignored rewrite (%s): %s",
ruleptr->nrule, accerr, newstr);
}
free(newstr);
was_match = 0;
break;
}
free(current);
current = newstr;
if (verbosity >= 3) {
syslog(LOG_INFO, "remap: rule %d: rewrite: %s",
ruleptr->nrule, current);
}
} else if (ruleptr->rule_flags & RULE_HASFILE) {
if (pf->f_validate(current, mode == 'G' ? RRQ : WRQ,
pf, &accerr)) {
if (verbosity >= 3) {
syslog(LOG_INFO, "remap: rule %d: not exiting (%s)\n",
ruleptr->nrule, accerr);
}
was_match = 0;
break;
}
}
} else {
break; /* No match, terminate unconditionally */
}
@ -426,7 +460,7 @@ char *rewrite_string(const char *input, const struct rule *rules,
if (was_match) {
was_match = 0;
if (ruleptr->rule_flags & RULE_EXIT) {
if (ruleptr->rule_flags & (RULE_EXIT|RULE_HASFILE)) {
if (verbosity >= 3) {
syslog(LOG_INFO, "remap: rule %d: exit",
ruleptr->nrule);